Prostate cancer is the second most common cause of cancer-related death among men in the United States. The PI3K-AKT-mTOR pathway is highly deregulated in prostate cancer. An outstanding and poorly understood question is the contribution of the most downstream signaling components of this pathway, 4EBP-eIF4E and p70S6Ks that control gene expression at the translation level towards prostate cancer development. The significance of this question is underscored by the tremendous therapeutic potential for targeting downstream translational components of mTOR signaling in human cancer. In this proposal, we employ a novel pharmacogenomic approach that will allow us to delineate specific steps in protein synthesis control that impinge on post-genomic control of prostate cancer development and therapeutic response, which has not been previously possible due to a lack of appropriate genetic and molecular tools. Specifically, we have designed and validated in vivo animal models to functionally restore the activity of 4EBP-eIF4E, p70S6K1 and rpS6 to normal levels in the setting of oncogenic mTOR hyperactivation. Furthermore, we will use the first ATP active site inhibitors of mTOR, which we have developed and characterized, to pharmacologically interrogate the downstream translational components of mTOR in prostate cancer initiation, progression and therapeutic response. In the context of PTEN-mediated prostatic intraepithelial neoplasia (PIN), our preliminary findings show that these inhibitors exhibit the strongest effect on aberrant mTOR dependent protein synthesis known to date and lead to the complete regression of this neoplastic lesion. This is further substantiated by the ability of these inhibitors to induce cell cycle arrest and programmed cell death in human prostate cancer cells. In addition, we have successfully optimized and employed a novel technology for examining translation of the prostate cancer genome, known as ribosome profiling (RP). This led to the first functional genome-wide analysis of the translational state of prostate cancer modulated by oncogenic mTOR signaling, which lays the groundwork for experiments proposed in this grant. Together, our current proposal, which utilizes a convergence of state-of-the-art genetic mouse models, novel mTOR inhibitors, and translation profiling, will provide an unprecedented level of insight into the post-genomic mechanisms of prostate cancer development dictated at the level of protein synthesis control. Moreover, these studies will identify novel functional biomarkers for mTOR hyperactivity that may aid in predicting clinical outcomes as well as provide the preclinical rationale for targeting the most downstream translational components of mTOR signaling in human prostate cancer.